Pirfenidone, an antifibrotic drug, has antitumor potential against different types of cancers. Our work explored whether pirfenidone sensitizes non-small cell lung cancer (NSCLC) cell lines to chemotherapeutic treatments. The cytotoxic effect of paclitaxel in combination with pirfenidone against three NSCLC cell lines (A549, NCI-H322 and NCI-H460) was evaluated using the sulforhodamine B assay. The effects of this combination on cell viability (trypan blue exclusion assay), proliferation (BrdU incorporation assay), cell cycle (flow cytometry following PI staining) and cell death (Annexin V-FITC detection assay and Western blot) were analyzed on the most sensitive cell line (NCI-H460). The cytotoxic effect of this drug combination was also evaluated against two non-tumorigenic cell lines (MCF-10A and MCF-12A). Finally, the ability of pirfenidone to sensitize NCI-H460 cells to a combination of paclitaxel plus carboplatin was assessed. The results demonstrated that pirfenidone sensitized NCI-H460 cells to paclitaxel treatment, reducing cell growth, viability and proliferation, inducing alterations in the cell cycle profile and causing an increase in the % of cell death. Remarkably, this combination did not increase cytotoxicity in non-tumorigenic cells. Importantly, pirfenidone also sensitized NCI-H460 cells to paclitaxel plus carboplatin. This work highlights the possibility of repurposing pirfenidone in combination with chemotherapy for the treatment of NSCLC.

Drug repurposing in cancer emerged as a strategy to identify antitumor potential in drugs clinically approved for the treatment of other diseases, offering new treatment possibilities especially for cancers with limited therapeutic alternatives, as the non-small cell lung cancer (NSCLC). Currently, vinorelbine, an anti-mitotic drug, is used for the treatment of NSCLC. The combination of vinorelbine with repurposed drugs that may increase its efficacy, with a tolerable safety profile, is an attractive therapeutic approach. Pirfenidone, an approved anti-fibrotic drug, has been previously demonstrated to sensitize different cancer cells to the effect of some anti-cancer agents. Therefore, our work aimed to assess the potential off-target effect of pirfenidone as a chemosensitizer of NSCLC cells to Vinorelbine. Treatment of NCI-H460 NSCLC cells with pirfenidone enhanced the sensitivity of these cells to vinorelbine (determined with the Sulforhodamine B assay). This was verified in cells treated with the GI50 concentration of Pirfenidone (2mM) with the following concentrations of vinorelbine: 7nM (GI50), 3.5 nm and 1.75 nm. The strongest combination treatment increased the % of cells in the G1 phase of the cell cycle (determined by flow cytometry) and reduced cell proliferation (assessed with the BrdU assay). Importantly, the combined treatment (vinorelbine 7nM and pirfenidone 2mM) did not show toxicity in non-tumorigenic MCF10A cells. Future work will validate these results in other cell lines and in xenograft mice models of NSCLC, to evaluate the possibility of repurposing pirfenidone for the treatment of NSCLC in combination with Vinorelbine approved regimens.